In known devices of the kind referred to above (German Pat. No. 2,047,774) the flexible spreader elements consist of link chains which are tensioned outwardly for forming the filling aperture at the respective bag. The adjuster means tensioning the respective link chain outwardly consists of an arcuate member provided with a traction rod, the member engaging the chain approximately in the centre of the filling aperture and pulling the same outwardly perpendicularly to the conveyance direction of the bags connected together like a band. This device comprises certain disadvantages. Since the flexible spreader elements are formed by chains, a rhombus-like filling aperture is produced upon tensioning the chains outwardly. Because of this rhombus-like filling aperture, acute deflections of the aperture edges of the bags occur at the corners of this rhombus, which may lead to damage to the bag material. Moreover the chain links subject the bag material likewise to considerable stress, namely even when the chains are provided with travelling driver members. These driver members lead to the further disadvantage that the chains must be constructed in a relatively complicated manner and thereby are expensive.
Furthermore the stressing referred to of the aperture edges of the bags limits the conveyance speed of the bags and thereby the processing speed of the apparatus.